<template>
  <div class="xtx-numbox">
    <div class="label">数量</div>
    <div class="numbox">
      <a href="javascript:;" @click="dec">-</a>
      <input type="text" :value="Num">
      <!-- <input type="text" readonly :value="Num"> -->
      <a href="javascript:;" @click="add">+</a>
    </div>
  </div>
</template>
<script>
import { ref, watch } from 'vue'
export default {
  name: 'XtxNumbox',
  props: {
    max: {
      type: Number
    },
    min: {
      type: Number
    },
    modelValue: {
      type: Number,
      default: 1
    }
  },
  setup (props, { emit }) {
    const Num = ref(1)
    // 点击加号
    function add () {
      if (Num.value === props.max) return
      Num.value++
      // 抛出事件 并传入修改后的值
      // vue2 input事件
      // vue3 update:modelvalue 事件
      emit('update:modelValue', Num.value)
      emit('change', Num.value)
    }
    // 点击减号
    function dec () {
      if (Num.value === props.min) return
      Num.value--
      emit('update:modelValue', Num.value)
      emit('change', Num.value)
    }
    // 使用v-model实现默认显示的商品数量为动态的
    watch(
      () => props.modelValue,
      () => { Num.value = props.modelValue },
      { immediate: true })
    watch(() => Num.value,
      (newValue) => {
        if (newValue > props.max) {
          Num.value = props.max
        }
        if (newValue < props.min) {
          Num.value = props.min
        }
      })
    return {
      Num,
      add,
      dec
    }
  }
}
</script>
<style scoped lang="less">
.xtx-numbox {
  display: flex;
  align-items: center;
  .label {
    width: 60px;
    color: #999;
    padding-left: 10px;
  }
  .numbox {
    width: 120px;
    height: 30px;
    border: 1px solid #e4e4e4;
    display: flex;
    > a {
      width: 29px;
      line-height: 28px;
      text-align: center;
      background: #f8f8f8;
      font-size: 16px;
      color: #666;
      &:first-of-type {
        border-right:1px solid #e4e4e4;
      }
      &:last-of-type {
        border-left:1px solid #e4e4e4;
      }
    }
    > input {
      width: 60px;
      padding: 0 5px;
      text-align: center;
      color: #666;
    }
  }
}
</style>
